Histology Test 1 — Questions and Answers

Question 1: An oophorectomized monkey is treated with high doses of estrogen. Which of the following changes is most likely to occur in the endometrium after 1 year of treatment?

Atrophy
Hyperplasia (Correct answer)
Hypertrophy
Hypoplasia
Metaplasia

Correct answer: Hyperplasia

Estrogen is a potent mitogen for endometrial cells, stimulating their proliferation. In an oophorectomized monkey, the absence of endogenous progesterone to counterbalance estrogen's effects, combined with high doses of exogenous estrogen, will lead to continuous stimulation of endometrial cell division. This sustained proliferation results in an increase in the number of endometrial cells, a process known as hyperplasia.

Question 2: Which of the following muscle cell components helps spread the depolarization of the muscle cell membranes throughout the interior of muscle cells?

Actin
Myosin
T tubule (Correct answer)
Tropomyosin
Troponin
Z disk

Correct answer: T tubule

T-tubules (transverse tubules) are invaginations of the muscle cell membrane (sarcolemma) that penetrate deep into the muscle fiber. Their primary function is to rapidly transmit the action potential (depolarization) from the sarcolemma to the interior of the muscle cell, ensuring that all myofibrils contract simultaneously. This allows for efficient and coordinated muscle contraction.

Question 3: A new drug is developed that prevents the demyelinization occurring in the progress of multiple sclerosis. The drug protects the cells responsible for the synthesis and maintenance of myelin in the central nervous system. These cells are most likely which of the following?

Astrocyte
Ependymal cell
Microglial cell
Oligodendrocyte (Correct answer)
Schwann cell

Correct answer: Oligodendrocyte

Oligodendrocytes are the glial cells responsible for synthesizing and maintaining the myelin sheath in the central nervous system (CNS). Myelin insulates axons, allowing for rapid and efficient nerve impulse conduction. In multiple sclerosis, the immune system attacks and damages myelin in the CNS, leading to demyelination. Therefore, a drug protecting these cells would target oligodendrocytes.

Question 4: A 10-year-old boy undergoes an appendectomy. Granulation tissue develops normally at the incision site. Tissue remodeling begins at this site with degradation of collagen in the extracellular matrix by which of the following proteins?

Cytokines
Lipoxygenases
Metalloproteinase (Correct answer)
Nitric oxide
Plasminogen activator

Correct answer: Metalloproteinase

Tissue remodeling, including the degradation of collagen and other extracellular matrix components, is primarily carried out by a family of enzymes called matrix metalloproteinases (MMPs). These zinc-dependent endopeptidases break down various components of the extracellular matrix, including collagen, playing a crucial role in wound healing, tissue development, and disease processes.

Question 5: In which of the following nuclear structures is DNA actively transcribed to rRNA?

Envelope
Lamina
Matrix
Nucleolus (Correct answer)
Pore

Correct answer: Nucleolus

The nucleolus is a distinct sub-organelle within the nucleus primarily responsible for the synthesis of ribosomal RNA (rRNA) and the assembly of ribosomal subunits. It contains the ribosomal DNA (rDNA) genes, which are actively transcribed into rRNA by RNA polymerase I. Therefore, the nucleolus is the specific site where DNA is actively transcribed to rRNA.

Question 6: A 22-year-old man is brought to the emergency department in respiratory distress 15 minutes after he was stung on the arm by a wasp. His pulse is 100/min, respirations are 30/min, and blood pressure is 100/60 mm Hg. Physical examination shows grunting respirations and subcostal retractions. Expiratory wheezes are heard over both lung fields. There is generalized urticaria. Secretion of the molecule causing this patient’s symptoms is most likely mediated by which of the following?

Activation of complement
Activation of mast cell (Correct answer)
Activation of T lymphocytes
Production of IgA
Production of IgG
Production of IgM

Correct answer: Activation of mast cell

The patient's symptoms (respiratory distress, wheezing, urticaria, hypotension) after a wasp sting are characteristic of anaphylaxis, a severe, systemic allergic reaction. This reaction is primarily mediated by the rapid degranulation of mast cells and basophils, which release potent inflammatory mediators like histamine. This release is typically triggered by the binding of an allergen to IgE antibodies on the surface of these cells.

Question 7: A 66-year-old man with Zollinger-Ellison syndrome undergoes a gastrectomy. He is informed that he will require treatment with intramuscular vitamin B12 (cyanocobalamin) for the rest of his life. This therapy is necessary because this patient lacks which of the following types of cells?

Chief
G (gastrin)
Goblet
Mucous neck
Parietal (Correct answer)

Correct answer: Parietal

Zollinger-Ellison syndrome involves excessive gastrin production, leading to hypersecretion of gastric acid. A gastrectomy removes the stomach, which contains the parietal cells. Parietal cells are responsible for secreting intrinsic factor, a glycoprotein essential for the absorption of vitamin B12 (cobalamin) in the terminal ileum. Without parietal cells and intrinsic factor, dietary vitamin B12 cannot be absorbed, necessitating lifelong intramuscular supplementation.

Question 8: Beginning with protein synthesis in membrane-bound ribosomes, hepatocytes secrete proteins into the circulation via which of the following mechanisms?

Active transport through the cell membrane
Diffusion through the cell membrane
Transport by microtubules and exocytosis
Transport in vesicles and exocytosis (Correct answer)
Transport through pores in the cell membrane

Correct answer: Transport in vesicles and exocytosis

Proteins destined for secretion, like those secreted by hepatocytes into the circulation, are synthesized on ribosomes attached to the endoplasmic reticulum. They then enter the ER lumen, undergo folding and modification, and are transported to the Golgi apparatus. In the Golgi, they are further processed, sorted, and packaged into secretory vesicles, which then fuse with the plasma membrane to release their contents outside the cell via exocytosis.

Question 9: Which of the following is required to transport fatty acids across the inner mitochondrial membrane?

Acyl carrier protein
Albumin
Carnitine (Correct answer)
Chylomicrons
Creatinine
Lecithin-cholesterol acyltransferase

Correct answer: Carnitine

Long-chain fatty acids cannot directly cross the inner mitochondrial membrane for beta-oxidation. They require a specialized transport system involving carnitine. Fatty acids are transferred to carnitine by carnitine palmitoyltransferase I (CPT-I) to form acylcarnitine, which is then transported across the inner mitochondrial membrane by the carnitine-acylcarnitine translocase. Inside the mitochondrial matrix, CPT-II transfers the fatty acid back to CoA, releasing carnitine and allowing beta-oxidation to proceed.

Question 10: An experiment is conducted in which the mitochondrial content of various tissues is studied. It is found that the mitochondrial content is directly proportional to the amount of energy one cell is required to generate and expend. The mitochondrial content is most likely greatest in which of the following types of cells?

Cardiac muscle cells (Correct answer)
Chondrocytes
Endothelial cells
Epidermal cells
Hepatocytes
Osteocytes
White adipocytes

Correct answer: Cardiac muscle cells

Mitochondria are the primary sites of ATP production through oxidative phosphorylation. Cells with high energy demands, requiring continuous and substantial ATP generation, will have a greater mitochondrial content. Cardiac muscle cells are constantly contracting and require a massive and uninterrupted supply of energy to pump blood throughout the body, making them among the most metabolically active cells with an exceptionally high density of mitochondria.

Question 11: A 45-year-old man without a history of bleeding or excessive bruising dies suddenly due to rupture of an aortic dissection. Genetic analysis at autopsy shows a defect in the gene for fibrillin. Which of the following events most likely occurs with defective fibrillin?

Elastic fibers in the extracellular matrix are not correctly formed (Correct answer)
Hyaluronic acid in proteoglycans is not sulfated on the proper hydroxyl residues
Intermediate filaments are not assembled in endothelial cells
Shorter side chains of chondroitin sulfate are present on the proteoglycans
Tubulin is not polymerized correctly due to the lack of GTP in endothelial cells

Correct answer: Elastic fibers in the extracellular matrix are not correctly formed

Fibrillin is a major component of microfibrils, which are essential for the formation and integrity of elastic fibers in the extracellular matrix. A defect in the fibrillin gene, as seen in Marfan syndrome, leads to the production of abnormal fibrillin-1 protein. This results in weakened or improperly formed elastic fibers, particularly in tissues like the aorta, leading to conditions such as aortic dissection and rupture due to loss of structural integrity and elasticity.

Question 12: A 42-year-old woman comes to the physician for a follow-up examination after two separate Pap smears have shown dysplastic epithelial cells. Results of a molecular diagnostic test show DNA that encodes high-risk versions of the human papillomavirus E6 and E7 proteins. The viral E6 protein binds to the cellular p53 tumor suppressor gene, causing it to be degraded. Which of the following best describes the mechanism by which the E6 protein causes cervical cancer?

Arrests the cell cycle
Enhances tissue invasion and metastasis
Inhibits telomerase expression
Prevents apoptosis (Correct answer)
Sustains angiogenesis

Correct answer: Prevents apoptosis

The p53 tumor suppressor protein is a critical regulator of the cell cycle and apoptosis. When DNA damage or cellular stress occurs, p53 can halt the cell cycle for repair or induce apoptosis if the damage is irreparable. By causing the degradation of p53, the HPV E6 protein removes this crucial checkpoint and pro-apoptotic signal, allowing damaged cells to continue proliferating and avoiding programmed cell death, thereby contributing to oncogenesis and cervical cancer development.

Question 13: A 90-year-old woman is brought to the emergency department 30 minutes after she fell while climbing the steps into her house. Physical examination shows tenderness over the right shin area. An x-ray of the right lower extremity shows a fracture of the tibia. A DEXA scan shows decreased bone density. Increased activity of which of the following cell types is the most likely cause of the decrease in bone mass in this patient?

Chondrocytes
Osteoblasts
Osteoclasts (Correct answer)
Osteocytes
Osteoprogenitor cells

Correct answer: Osteoclasts

Osteoclasts are specialized cells responsible for bone resorption, which is the breakdown of bone tissue. In an elderly patient with decreased bone density (osteoporosis), there is an imbalance where the activity of osteoclasts in breaking down bone exceeds the bone formation by osteoblasts. This leads to a net loss of bone mass, making the bones fragile and prone to fractures. Chondrocytes form cartilage, osteoblasts build bone, osteocytes maintain bone, and osteoprogenitor cells are precursors to osteoblasts.

Question 14: A 50-year-old man comes to the physician because of a cough productive of large quantities of mucus for 6 months. He has smoked 1 pack of cigarettes daily for 25 years. Which of the following cell types is the most likely cause of the increase in this patient’s secretion of mucus?

Columnar ciliated epithelial cells
Goblet cells (Correct answer)
Interstitial cells
Macrophages
Pneumocyte epithelial cells

Correct answer: Goblet cells

Goblet cells are specialized epithelial cells found in the respiratory tract that are responsible for producing and secreting mucus. Chronic irritation from smoking, as seen in this patient with chronic bronchitis, causes hypertrophy and hyperplasia of these cells. This increase in goblet cell number and size leads to excessive mucus production, which is characteristic of a productive cough in chronic bronchitis. Columnar ciliated epithelial cells help move mucus, but goblet cells are the primary producers.

Question 15: A 65-year-old man with severe atherosclerotic coronary artery disease comes to the emergency department because of a 12-hour history of chest pain. Plasma activity of the MB isozyme of creatine kinase (MB-CK) is markedly increased. Which of the following processes is the most likely explanation for the increased plasma MB-CK?

Cell membrane damage (Correct answer)
Endoplasmic reticulum dilation
Mitochondrial swelling
Polysome dissociation
Sodium pump dysfunction

Correct answer: Cell membrane damage

Creatine kinase-MB (CK-MB) is an intracellular enzyme found predominantly in cardiac muscle cells. When myocardial cells suffer irreversible injury, such as during a myocardial infarction due to severe atherosclerosis, their cell membranes become damaged and lose integrity. This loss of membrane integrity allows intracellular components, including CK-MB, to leak out into the bloodstream, leading to a detectable increase in plasma activity. The other options describe intracellular changes that may occur but are not the direct cause of enzyme release into the plasma.

Question 16: During an experimental study, an investigator finds that the regulation of cell cycle and programmed cell death may be initiated by the mitochondrion. The interaction of the mitochondrion with the activation of the caspase family of proteases and subsequent apoptosis is most likely mediated by which of the following?

Calcium release
cAMP production
Cytochrome c release (Correct answer)
GTP binding
Nitric oxide release

Correct answer: Cytochrome c release

The mitochondrion plays a central role in initiating the intrinsic pathway of apoptosis. Upon receiving apoptotic signals, the outer mitochondrial membrane becomes permeable, leading to the release of cytochrome c from the intermembrane space into the cytosol. Cytosolic cytochrome c then binds to Apaf-1, forming the apoptosome, which activates caspase-9 and subsequently the effector caspases, leading to programmed cell death. While calcium can influence mitochondrial function, cytochrome c release is the direct mediator for caspase activation in this pathway.

Question 17: A 48-year-old man has hepatic cancer that is unresponsive to standard therapy. He enrolls in a clinical study of a novel chemotherapeutic agent that, as a side effect, blocks kinesin, a component of the cellular microtubular transport system. One week later, he develops skeletal muscle weakness. An alteration in which of the following components of the neuromuscular junction is the most likely cause of the muscle weakness?

A decrease in the number of postsynaptic neurotransmitter receptors
A decrease in the number of presynaptic neurotransmitter vesicles (Correct answer)
A decrease in the presynaptic neuron calcium permeability
Impaired α-motoneuron action potential conduction
Impaired skeletal muscle action potential conduction

Correct answer: A decrease in the number of presynaptic neurotransmitter vesicles

Kinesin is a motor protein that uses microtubules to transport vesicles, including neurotransmitter vesicles, from the neuronal cell body down the axon to the presynaptic terminal. Blocking kinesin would impair this axonal transport, leading to a reduced number of neurotransmitter vesicles available for release at the neuromuscular junction. Fewer vesicles mean less neurotransmitter release, resulting in impaired muscle contraction and weakness. The other options describe different mechanisms of neuromuscular junction dysfunction not directly related to kinesin's role in vesicle transport.

Question 18: A polysome is actively involved in translation. The ribosomes are attached to which of the following?

Single-stranded DNA
Double-stranded DNA
mRNA (Correct answer)
rRNA
tRNA

Correct answer: mRNA

A polysome, or polyribosome, is a complex formed by multiple ribosomes simultaneously translating a single messenger RNA (mRNA) molecule. The ribosomes move along the mRNA strand, each synthesizing an identical polypeptide chain. This arrangement allows for the efficient and rapid production of many copies of a specific protein from a single mRNA template. DNA is the genetic blueprint, and rRNA and tRNA are components of the translational machinery but are not the template for protein synthesis.

Question 19: A pathologist uses monoclonal antibodies against several intermediate filament proteins and finds that a tumor section stains positive for cytokeratin only. The tumor most likely originated from which of the following tissues?

Connective
Epithelial (Correct answer)
Glial
Muscle
Nemal

Correct answer: Epithelial

Intermediate filaments are cell-type specific cytoskeletal components that are highly useful in tumor diagnosis. Cytokeratins are the characteristic intermediate filaments found exclusively in epithelial cells and their malignant tumors (carcinomas). Therefore, a tumor section staining positive for cytokeratin indicates that the tumor originated from epithelial tissue. Other intermediate filaments like vimentin (mesenchymal), desmin (muscle), and GFAP (glial) are specific to different cell types.

Histology Test 1

An oophorectomized monkey is treated with high doses of estrogen.
Which of the following changes is most likely to occur in the endometrium after 1 year of treatment?